Not Applicable.
The invention relates to oxygen concentrators for supplying medical oxygen to a patient and to fill a portable oxygen container.
Oxygen concentrators are commonly used for supplying supplemental oxygen to patients for medical purposes. Typically, an oxygen concentrator includes an air compressor which delivers a flow of pressurized, filtered air to a molecular sieve bed which passes oxygen while blocking the flow of nitrogen. The oxygen enriched air at an output from the molecular sieve bed is typically about 90% to 95% pure oxygen, with the remainder being primarily argon. The oxygen enriched air may be stored in an accumulator prior to delivery to a patient through a nasal cannula. Preferably, two molecular sieve beds are provided to achieve a continuous flow of oxygen enriched air. While one of the molecular sieve beds is separating nitrogen from air to produce oxygen enriched air, a reverse flow of oxygen enriched air is passed through the other molecular sieve bed to purge previously separated nitrogen from the molecular sieve bed. Periodically, the operating modes of the two molecular sieve beds are switched.
Recently, oxygen concentrators have been used to supply oxygen enriched air simultaneously to a patient and to a compressor or other pressure intensifier for filling a portable oxygen cylinder. The portable oxygen cylinder is used as a portable oxygen source, allowing the patient to be ambulatory. The oxygen concentrator must be sized to have a capacity to deliver more oxygen enriched air than is needed by the patient. The excess oxygen enriched air is compressed to a pressure as high as 3000 psig and the compressed oxygen enriched air is stored in the portable oxygen cylinder. Apparatus using an oxygen concentrator simultaneously for supplying a patient""s supplemental oxygen needs and for filling a gaseous oxygen cylinder is illustrated, for example, in U.S. Pat. Nos. 5,858,062 and 5,988,165. Such apparatus is designed to prioritize the usage of the available oxygen enriched air so that oxygen enriched air at a sufficiently high flow rate and/or at a sufficient concentration level is continuously delivered to the patient before any oxygen enriched air can be delivered to the compressor for filling a cylinder.
It is also known that the oxygen enriched air from an oxygen concentrator can be compressed and chilled to the point that it is liquefied for filling portable dewars sometimes used by ambulatory patients requiring supplemental oxygen. As used herein, the term xe2x80x9ccylinderxe2x80x9d is intended to include both portable gaseous oxygen cylinders and portable dewars for holding liquefied oxygen.
It is now well known that delivering a continuous flow of supplemental oxygen to a patient is wasteful of oxygen. Only the oxygen delivered to the patient during the initial part of the inhalation time reaches the portions of the patient""s lungs where the oxygen is used by the patient. Oxygen in the trailing portion of the inhalation cycle remains in the portions of the patient""s airway where it is not used. Also, any oxygen delivered to the patient while the patient exhales flows to the atmosphere without any benefit to the patient. Oxygen dose flow controllers are well known for conserving oxygen by delivering a short duration oxygen dose either only during inhalation or only during the initial portion of the inhalation cycle. Such flow controllers are shown, for example, in U.S. Pat. Nos. 5,370,112, 4,971,049, 4,519,387, 4,462,398, 4,461,293 and 4,457,303. Typically, the dose flow controllers either sense or anticipate the beginning of inhalation and deliver a short duration dose of oxygen which lasts for no more than the inhalation time and frequently for less than the entire inhalation time. When a dose flow controller is used by an ambulatory patient with a portable oxygen source, the oxygen source can supply oxygen for at least twice the time as apparatus which supplies a continuous flow of oxygen. Alternately, a dose flow controller can be used with a smaller capacity oxygen source, such as a smaller and lighter cylinder for portability or a smaller capacity oxygen concentrator.
The one embodiment of the invention is directed to a medical oxygen concentrator suitable for supplying medical oxygen alternately to a patient and to a compressor for filling an oxygen cylinder for portable use by the patient. The oxygen concentrator is sized to have a continuous output flow rate at a concentration level which at least meets the needs of the patient. The output from the concentrator is delivered to a dose flow controller which senses when the beginning of a patient inhalation and momentarily opens a valve to deliver a dose of oxygen enriched air to the patient. During the time that the oxygen concentrator is not delivering a dose of oxygen enriched air to the patient, the flow controller delivers the oxygen enriched air from the oxygen concentrator to a cylinder filler circuit, such as a compressor and/or chiller for filling an oxygen cylinder with gaseous or liquefied oxygen enriched air. When patient inhalation is again sensed, delivery of oxygen enriched air from the concentrator to the cylinder filler circuit is interrupted and another oxygen dose is delivered to the patient. Preferably, the oxygen enriched air intermittently delivered to the cylinder filler circuit is at a greater flow rate than that continuously used by the compressor. The excess oxygen enriched air is accumulated to provide a continuous source of oxygen enriched air for the compressor. Alternately, the compressor can be controlled in response to the amount of oxygen enriched air available.
According to a further embodiment of the invention, a cylinder filler oxygen concentrator is provided with fail safe features for accommodating a patient""s continuing oxygen needs. The oxygen concentrator is adapted to supply supplemental oxygen enriched air to the patient and for filling a cylinder. In the event of an operation failure of the oxygen concentrator, a valve may be opened to supply supplemental oxygen enriched air from the previously filled cylinder to the patient and an alarm may be sounded to call for help or to alert the patient. If a dose flow controller is used for controlling delivery of oxygen enriched air to the patient, a backup battery may be provided to extend the time that the cylinder can provide oxygen enriched air to the patient. Further, the dose flow controller also may be failsafe through a design which established a continuous flow of oxygen enriched air to the patient in the event of dose flow controller failing.
Various objects and advantages of the invention will become apparent from the following detailed description of the invention and the accompanying drawings.